| Abstract: | Controlled proteolysis of epidermal growth factor from the mouse leads to fragments of mouse epidermal growth factor containing residues 1-48 and 1-45. The COOH-terminal pentapeptide appears to play a crucial role in determining the hydrophobic interactions between the hormone and the stationary phase during gel chromatography on TSK-125 gel. Proton NMR studies indicate that the overall structure of mouse epidermal growth factor is retained in the protein devoid of the COOH-terminal pentapeptide, while subsequent cleavage of the peptide bond between Arg-45 and Asp-46 starts to perturb the proton resonances most characteristic of the tertiary structure of the hormone, especially those from the aromatic ring protons of Tyr-37. Consequently, photochemically induced dynamic nuclear polarization experiments show an increased exposure of Tyr-37 in the fragment of mouse epidermal growth factor containing residues 1-48. Nuclear Overhauser data suggest that structural changes do occur on fragmentation but seem to be localized in the tiered-beta-sheet domain which contains Tyr-37. |
